
This is equivalent to [1]}
\(p_{MM}^* &= \max _{\mathbf {V}_i} -\sum _{i=1}^n\mathcal {L}^* \left(\mathbf {V}_i,\mathbf {Y}_i \right) \nonumber \\\text{s.t.} &~ \max _{\begin{array}{c}\Vert \mathbf {W}_1\Vert _F\le 1\end{array}} \left\Vert \sum _{i=1}^n (\mathbf {I}_d \otimes \mathbf {V}_i^T)(({\mathbf {X}}_i^\top \otimes \mathbf {I}_s)\mathbf {vec}(\mathbf {W}_1)_+ \right\Vert _F \le \beta \) 
